The typical 30 year old loses half of his or her muscle mass by the time they’re 90, according to Forbes. Building muscle has many health benefits that can even extend your life. Muscles give us strength, mobility and balance, protect our joints and ligaments, reduce the chance of injury, they give us higher metabolisms so we can control our weight, and they even reduce your chances of developing a chronic terminal disease. Harvard School of Public Health recommends adults strength train all their muscle groups twice a week to maintain strong muscles over time, and to improve longevity.

Healthier Weight and Metabolism

According to Harvard, a sedentary lifestyle increases your chances of becoming overweight as your muscles wither away and your metabolism slows. According to "Oprah" magazine, as compared to non-lifters, lifters burn more fat and are more likely to keep their weight off because they have higher metabolisms. Weight lifting also burns calories while you're lifting. Doing just one weight-lifting circuit with eight exercises, which takes you about eight minutes, expends about 160 to 230 calories.

Lower Risk of Life-Shortening Chronic Diseases

One of the major ways weight lifting can help you live longer is by lowering your risks of developing several common chronic fatal diseases. A study at the University of Michigan found that doing three workouts per week, while targeting all your body's muscle groups for two months, reduces blood pressure enough to lower your risk of heart attack by 15 percent and your risk of stroke by 40 percent. A 6-month University of Florida study found that weight lifters have a lower risk of developing cancer due to having less oxidative cell damage -- which can lead to cancer -- than non-lifters. Strength-training reduces your risk of colon cancer also by speeding up the rate food moves through your large intestine by as much as 56 percent.

Stronger Bones

Your bones need resistance just like your muscles in order to grow back stronger and increase their density. By increasing the density or mass of your bones, you lower your risk of developing osteoporosis. After you turn 40, your bone mass will start to decrease by about 1 percent each year, making osteoporosis, the loss of bone mass, a big risk as we age. If you develop osteoporosis, a minor fall can cause a bone fracture or break. Hip fractures can cause death or confine you to a wheel chair for the rest of your life, making it hard for you to exercise for your health and longevity.

Maintaining Muscles Keeps Your Body Young

Your muscle mass decreases as you age, as much as 10 percent between the ages of 30 and 50. Muscles are responsible for your metabolism and energy, strength and power, as well as speed and agility. Maintaining your muscles can help you stand up and sit down, walk and do other things without being slowed down by underused muscles. Lifting heavy weights slowly and lifting lighter weights at a quick pace are particularly effective for improving your muscle function and speed of movement.

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About the Author

Lindsay Haskell enjoys writing about fitness, health, culture and fashion. She is a contributor for "Let's Talk Magazine" and "The Wellesley News." Haskell is completing her B.A. in philosophy at Wellesley College. She's also a fiction writer whose work can be read online.